A multiconductor transmission line model for grounding grids

•New approach for modeling surge propagation in grounding grids and its surroundings.•Based on multiconductor transmission line theory, modal analysis and two port networks.•Calculates the surge distribution in the grid and soil surface, the transient step and touch voltages.•The algorithm was successfully tested and compared with measurements and other techniques. In this paper, a new approach for modeling grounding grids excited by lightning currents is proposed. The model is based on considering each set of parallel conductors in the grounding grid as a multiconductor transmission line. Electrical parameters are calculated and modal analysis is used in order to obtain a two port network representation for each set of parallel conductors in the grid. The different two port networks are interconnected following the pattern of connections in the grid; then, the system equations are reduced in order to obtain currents and voltages in the different grid junctions. This approach facilitates calculating the transient leakage currents into the soil and therefore the induced voltage on the soil surface. Finally, the transient step and touch voltages are calculated. The computer model was validated by means of an extensive comparison between obtained results with the proposed model, measurements and calculated results published in the literature. The validation process was extended successfully to grounding grids and vertical and horizontal electrodes.